This application claims priority to Japanese Patent Application No. 2001-265369, filed on Sep. 3, 2001, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a marine engine. More particularly, preferred embodiments provide an improved air induction system for a marine engine that enables easy and smooth operation of a watercraft near a dock.
2. Description of the Related Art
Personal watercraft are designed to be relatively small and maneuverable, and are usually capable of carrying one to three riders. These craft commonly include a relatively small hull that defines a rider""s area above an engine compartment. The rider""s area normally includes a seat. A forward portion of the rider""s area also normally includes a steering handle, which normally has an attached throttle lever.
The engine compartment contains an internal combustion engine that powers a jet propulsion unit. The engine includes an air induction system for delivering air into one or more combustion chambers. The engine also includes an exhaust system for expelling exhaust gases from the combustion chambers to the body of water in which the watercraft operates.
The jet propulsion unit, which includes an impeller, is positioned within a tunnel formed on an underside of the hull behind the engine compartment. An impeller shaft, which is driven by the engine, usually extends between the engine and the jet propulsion device through a bulkhead of the hull tunnel. Rotation of the impeller discharges water rearwardly of the watercraft through a steering nozzle, propelling the watercraft. The rider controls the speed of the watercraft by varying the rate of water discharge through the steering nozzle via the throttle lever.
A deflector within the steering nozzle controls a direction of water discharge from the steering nozzle, thus controlling a direction of travel of the watercraft. An orientation of the deflector corresponds to an orientation of the steering handle. Thus, to turn the watercraft, the rider turns the steering handle, which turns the deflector.
The preferred embodiments of the induction system for marine engine have several features, no single one of which is solely responsible for their desirable attributes. Without limiting the scope of this induction system as expressed by the claims that follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled xe2x80x9cDetailed Description of the Preferred Embodiments,xe2x80x9d one will understand how the features of the preferred embodiments provide advantages, which include the ability to make fine adjustments of watercraft speed and direction at low engine speeds.
When docking the watercraft, smooth control and the ability to make fine adjustments in speed and direction are advantageous. However, in order to turn the watercraft, water must be discharged from the steering nozzle. Thus, the rider must carefully manipulate the steering handle and the throttle lever simultaneously to control the direction and speed of the watercraft. Such control is difficult at low engine speeds, such as when docking, because very little water is discharged through the steering nozzle. Thus, one aspect of the present induction system for marine engine comprises the realization that present watercraft engines do not provide the ability to make fine adjustments to speed and direction at low engine speeds.
A preferred embodiment of the induction system for personal watercraft comprises a watercraft including a hull defining an engine compartment. An internal combustion engine is disposed within the engine compartment. The engine includes an engine body defining at least one combustion chamber, and an air induction system. The air induction system includes an air intake chamber having an inlet, at least one throttle body having an inlet end in fluid communication with the air intake chamber and at least one throttle valve providing selective fluid communication between the inlet end and the at least one combustion chamber. The air induction system further includes an air intake bypass device providing selective fluid communication between the air intake chamber and the at least one throttle body at a point downstream from the at least one throttle valve in a direction of air flow from the air intake chamber to the at least one combustion chamber. Additionally, the bypass device is responsive to a user-operable switch, and adjusts an air amount delivered to the engine based on an output of the user-operable switch.
Another preferred embodiment of the induction system for personal watercraft comprises a watercraft including a hull defining an engine compartment. An internal combustion engine is disposed within the engine compartment. The engine includes an engine body defining at least one combustion chamber, and an air induction system. The air induction system includes an air intake chamber having an inlet, at least one throttle body having an inlet end in fluid communication with the air intake chamber and at least one throttle valve providing selective fluid communication between the inlet end and the at least one combustion chamber. The air induction system further includes an air intake bypass device configured to guide intake air to the at least one throttle body at a point downstream from the at least one throttle valve in a direction of air flow from the air intake chamber to the at least one combustion chamber. A sensor is configured to sense when the watercraft approaches a dock. The bypass device is configured to increase an amount of air delivered to the engine based on the output of the sensor.
Another preferred embodiment of the induction system for personal watercraft comprises a four-cycle internal combustion engine comprising an engine body defining at least one combustion chamber. The engine further comprises an air intake chamber, and an air induction passage having an inlet end disposed in an interior of the air intake chamber. The induction passage extends from the inlet end to the at least one combustion chamber. A throttle valve is disposed within the induction passage. The engine further comprises an intake air bypass device. The bypass device includes a valve body having an air inlet, and at least one outlet for each cylinder in the engine.